An estimated 39.6 million people, including 8.5 million US Veterans (43%), are elderly and at risk for developing chronic sleep disturbance. Chronic sleep disturbance is associated with a number of negative health outcomes including cognitive decline, increased risk of fall, anxiety, and depressive disorders, contributing to the poor quality of life. The proposed research program will use a multi-disciplinary approach to examine: a) if a physiological decline or dysfunction of the preoptic hypothalamic (POAH) sleep- regulatory systems contribute to chronic sleep disturbance in aging; b) if chronic POAH inflammation and nitrosative stress in aging contribute to sleep-disturbance, by adversely affecting sleep-regulatory systems; and c) if sleep disturbance in aging can be mitigated by anti-inflammatory measures. Specific aim-1: will determine if the functional activity of sleep-regulatory median preoptic nucleus (MnPN) and ventrolateral preoptic area (VLPO) neurons decline with aging. We will compare in young vs. old rats: a) changes in discharge activity of sleep-active MnPN and VLPO neurons to spontaneous and homeostatic sleep cues (experiment-1); and b) c-Fos expression in VLPO and MnPN GABAergic neurons after different sleep pressures and sleep amounts (experiment-2). Specific aim-2: will determine if the MnPN and VLPO sleep-regulatory systems exhibit evidence of increased inflammation, nitrosative stress, and neuronal damage with aging. We will compare in young and old rats: a) microglia activation, and expression of TNF-alpha, iNOS, nitrotyrosine (markers of nitrosative stress), and markers of senescence, apoptosis and neuronal damage in the MnPN and VLPO GABAergic neurons, by immunohistochemistry (experiment-3); and b) levels of TNF-alpha, IL-6, iNOS, and nitrotyrosine by quantitative RT-PCR and Western blots as well as NO metabolites (nitrates and nitrites) and cytokine release in the MnPN and VLPO by ELISA and flourometry (experiment-4). Specific aim-3: will determine if chronic MnPN and VLPO inflammation contribute to sleep disturbance, by adversely affecting their sleep-regulatory neuronal systems. We will quantify: a) if chronic MnPN and VLPO inflammation, induced by local LPS infusion, in young rats produces sleep disturbance and immuno- histochemical changes in GABAergic neurons, that are typical of old age (experiment-5); and b) if chronic suppression of inflammation within the MnPN and VLPO, by focal infusion of minocycline, an inhibitor of microglia activity and a selective scavenger of peroxynitrite, reduces nitrosative stress in GABAergic neurons and improves sleep-wake organization and sleep continuity in aged rats (experiment-6). The proposed research program is conceptually innovative and will generate novel and fundamental data about the functional status of the POAH sleep-regulatory systems in aging. A better understanding of how CNS aging affects sleep-regulatory systems and the mechanism by which inflammation pathologically affects sleep-wake function may contribute to the development of novel preventative and therapeutic options for optimizing sleep health in the elderly including Veterans.